to a block of cork, insulated from each other; into a hole of
each carbon a pin of carbon fits loosely, projecting above the carbons;
another flat piece of carbon, having two holes in it, bridges over the
two lower carbons, being kept in its place by the pins of carbon which
fit loosely in the holes in it, the bottom carbons being connected with
the battery; a block of cork has a flat side of it cut out so as when
secured to the lower cork the carbons will not come in contact with it,
yet be close enough to it to keep the carbons from falling apart. The
cork covering the carbons forms a dome.

Any good telephone receiver when used in connection with this
microphone, reproduces articulate speech with remarkable distinctness,
especially hissing sounds, and with a loud and full tone.

A description of this microphone was published in _La Lumiere
Electrique_, of 15th April, 1882, and a drawing thereof on 29th April of
same year.

Another form of microphone is made as follows: Two blocks of gas carbon,
C, B, each about one and a half inches long and one inch square, having
each a circular hole one and a quarter inches deep and half inch in
diameter; these two blocks are embedded in a block of cork, C, about
one-quarter of an inch apart, these holes facing each other, each block
forming a terminal of the battery and induction coil; a pencil of
carbon, C, P, about three-eighths of an inch in diameter, and two inches
long, having a ring of ebonite, V, fixed around its center, is placed in
the holes of the two fixed blocks; the ebonite ring fitting loosely in
between the two blocks so as to prevent the pencil from touching the
bottom of the holes in the blocks. The space between the blocks is
closed with wax, W, to exclude the air, but not to touch the ring on the
pencil. A block of cork fitting close to the carbon blocks on all sides
is then firmly secured to the other block of cork. The microphone should
lie horizontally or at a slight angle.

This microphone produces in any good telephone perfect articulation in a
loud and full tone. In these microphones there is certainly "looseness
and delicacy of contact," and there is a "jolting or shaking motion,"
and it does not seem possible that there can be any "pressure of one
carbon against another."

I repeat the question I asked at the beginning of this communication,
and hope that it may elicit from you, or some of our scientific men, an
explanation of the theory of the act